Radar device and method for operating a radar device

ABSTRACT

The present invention relates to a radar device having means ( 10 ) for generating a carrier-frequency signal, means ( 12, 12   a,    12   b,    13, 13   a,    13   b ) for shaping pulses, means ( 14, 14   a,    14   b,    15, 15   a,    15   b ) for generating modulated radar pulses from the carrier-frequency signal, means ( 16, 18   a,    18   b,    18   c,    18   d ) for emitting modulated signals as radar pulses, means ( 18   a,    18   b,    18   c,    18   d ) for receiving radar pulses, and means ( 20 ) for processing the received radar pulses, the means for receiving the radar pulses having an array including a plurality of antennas ( 18   a,    18   b,    18   c,    18   d ), the means ( 20 ) for processing the radar pulses having means for dividing the signal power over at least two different reception branches ( 24, 26 ), and means ( 28   a,    28   b,    28   c,    28   d,    30   a,    30   b,    30   c,    30   d,    42 ) being provided for generating different directional characteristics ( 32, 34 ) in the various reception branches ( 24, 26 ). The invention also relates to a method for operating a radar device.

[0001] The present invention relates to a radar device having means forgenerating a carrier-frequency signal, means for shaping pulses, meansfor generating modulated radar pulses from the carrier-frequency signal,means for emitting modulated signals as radar pulses, means forreceiving radar pulses and means for processing the received radarpulses. The invention also relates to a method for operating a radardevice including the steps: generating a carrier-frequency signal,shaping pulses, generating modulated radar pulses from thecarrier-frequency signal, emitting the modulated signals as radarpulses, receiving radar pulses and processing the received radar pulses.

BACKGROUND INFORMATION

[0002] Numerous applications for radar devices are known in widelydiffering fields of technology. For example, the use of radar devices ispossible within the framework of the close-range sensor system in motorvehicles.

[0003] When working with radar devices, electromagnetic waves areradiated from a transmitting antenna. If these electromagnetic wavesstrike an obstacle, they are reflected, and after the reflection, arereceived again by a different or the same antenna. The received signalsare subsequently fed to a signal processing and signal analysis.

[0004] The endeavor is to collect and evaluate as much information aspossible about the vehicle surroundings. Such information concerns themeasurement of the distance of the motor vehicle to other objects, themeasurement of the relative speed between the vehicle and other objects,and an angle measurement with regard to the object to be detected. Ifpossible, these measurement objectives should be achieved with as low anexpenditure as possible for equipment, the effort being in particular torealize as many measurement objectives as possible in a single radardevice.

[0005] These efforts are especially problematic with regard to themeasurement of angle information, since here, according to the relatedart, a triangulation is performed on the basis of measured values from aplurality of spatially distributed sensors.

[0006] Possible applications for radar devices concern accidentprevention (“precrash”), ACC stop & go (“adaptive cruise control”), parkdistance control, semi-autonomous parking and detection of the blindspot.

SUMMARY OF THE INVENTION

[0007] The present invention is based on the radar device of thespecies, in that the means for receiving the radar pulses has an arrayincluding a plurality of antennas, the means for processing the radarpulses has means for dividing the signal power over at least twodifferent reception branches, and means are provided for generatingdifferent directional characteristics in the various reception branches.Using a radar device of this type, it is possible, for example, toimplement a precrash measurement and ACC stop & go simultaneously. Thegeneration of different directional characteristics makes it possible tocarry out an optimization with regard to the different demands in thevarious transmission branches. For example, a precrash measurement mustbe carried out in an extremely time-critical manner, while angleinformation, however, is of secondary importance.

[0008] In contrast thereto, in the case of ACC stop & go, an angularresolution is generally necessary. By making different directionalcharacteristics available, it is therefore possible to dispense withangle information in the reception branch for precrash, which permits anextremely time-critical measurement, while in the reception branch forACC stop & go, the directional characteristic is selected so that angleinformation is obtained.

[0009] Preferably, the means for emitting radar pulses has a widedirectional characteristic. In this way, the entire angular range to bedetected is covered.

[0010] The means for generating different directional characteristics inthe various reception branches preferably generates a swivellingdirectional characteristic in at least one reception branch. Thisreception branch in which the swivelling directional characteristic isgenerated may therefore-be used for transmitting the angle information.The possibility thus exists, for example, of using the reception branchfor ACC stop & go.

[0011] It may likewise be advantageous that the means for generatingdifferent directional characteristics in the various reception branchesgenerates a wide directional characteristic in at least one receptionbranch. For applications in which angle information is not of primaryimportance, a wide directional characteristic is sometimes sufficient.For example, the reception branch having the wide directionalcharacteristic may therefore be used for precrash.

[0012] It may likewise be advantageous that at least two differenttransmission branches are provided, and that means are provided forgenerating different directional characteristics in the varioustransmission branches. It is therefore possible to implement differentdirectional characteristics on the transmitter side, as well, and thusto support the advantageous effects of parallel operation for differentapplications of the radar device. This is particularly advantageous whenthe radar device uses the same antennas for transmitting and receiving.

[0013] The means for generating different directional characteristicspreferably has a control. Such a control receives, for example, signalsfrom the reception branches as input signals. It may also be responsiblefor the weighting in terms of amplitude and phase, and thus forgenerating the different directional characteristics.

[0014] Means are preferably provided for generating modulated signalsfrom the carrier-frequency signal, and means are provided for mixing thedelayed, modulated signals with received signals. The radar device maytherefore operate according to the correlation method. For instance, thedistance of a target object may be inferred by correlation on the basisof the time delay from the emission to the reception of the radarpulses.

[0015] It may likewise be preferred that the means for emitting theradar pulses be implemented as a single transmitting antenna. It is thussufficient that different directional characteristics are generated byan antenna array on the receiver end, while a single transmittingantenna is provided on the transmitter end.

[0016] However, it may also be useful if the means for emitting theradar pulses has an array including a plurality of antennas. Theseantennas may be positioned separate from the antenna array on thereceiver end, or they may be identical with the antenna array on thereceiver end. Thus, there is great flexibility within the scope of thepresent invention with respect to the layout of transmitting andreceiving antennas.

[0017] It may also be advantageous that means are provided forgenerating a high pulse repetition frequency, and that means areprovided for generating a low pulse repetition frequency. The differentpulse rates may therefore be utilized for different applications, thedifferent pulse repetition frequencies being used on the variousdirectional characteristics.

[0018] The means for generating a low pulse repetition frequencypreferably divides the high pulse repetition frequency by a wholenumber. Pulse repetition frequencies are thereby advantageouslyavailable which have an integer relationship. Generating the variouspulse repetition frequencies in this manner is also efficient.

[0019] It is particularly advantageous if the radar pulses having thewide directional characteristic are emitted with the high pulserepetition frequency, and the radar pulses with the swivellingdirectional characteristic are emitted with the low pulse repetitionfrequency. For example, during this operation it is possible to performthe time-critical measurement on the wide directional characteristicusing a high pulse repetition frequency, while for the swivellingdirectional characteristic, which is preferably less time-criticalwithin the framework of the present invention, it is possible to workwith the lower pulse repetition frequency.

[0020] It may likewise be useful if the radar pulses with the swivellingdirectional characteristic are emitted using a pulse repetitionfrequency that is modulated by a PN (“pseudo-noise”) code. When workingwith such a PN modulation, it is decided according to a PN code whethera pulse is sent or not. Since the PN code is known to the receiver, atarget object may be detected by correlation.

[0021] The present invention is based on the method of the species, inthat the radar pulses are received by an array having a plurality ofantennas, the signal power is divided over at least two differentreception branches, and different directional characteristics aregenerated in the various reception branches. Using a method of thistype, it is possible, for example, to implement a precrash measurementand ACC stop & go simultaneously. The generation of differentdirectional characteristics makes it possible to carry out anoptimization with regard to the different demands in the varioustransmission branches. For example, a precrash measurement must becarried out in an extremely time-critical manner, while angleinformation, however, is of secondary importance. In contrast thereto,in the case of ACC stop & go, an angular resolution is generallynecessary. By making different directional characteristics available, itis therefore possible to dispense with angle information in thereception branch for precrash, which permits an extremely time-criticalmeasurement, while in the reception branch for ACC stop & go, thedirectional characteristic is selected so that angle information isobtained.

[0022] It may be advantageous if the radar pulses are emitted with awide directional characteristic. In this way, the entire angular rangeto be detected is covered.

[0023] Preferably, a swivelling directional characteristic is generatedin at least one reception branch. This reception branch in which theswivelling directional characteristic is generated may therefore be usedfor transmitting the angle information. The possibility thus exists, forexample, of using the reception branch for ACC stop & go.

[0024] It may be advantageous if a wide directional characteristic isgenerated in at least one reception branch. For applications in whichangle information is not of primary importance, a wide directionalcharacteristic is sometimes sufficient. For example, the receptionbranch having the wide directional characteristic may therefore be usedfor precrash.

[0025] It may likewise be useful if different directionalcharacteristics are generated in the various transmission branches. Itis therefore possible to implement different directional characteristicson the transmitter side, as well, and thus to support the advantageouseffects of parallel operation for different applications of the radardevice. This is particularly advantageous when the radar device uses thesame antennas for transmitting and receiving.

[0026] The different directional characteristics are preferablygenerated by a control. Such a control receives, for example, signalsfrom the reception branches as input signals. It may also be responsiblefor the weighting in terms of amplitude and phase, and thus forgenerating the different directional characteristics.

[0027] It is particularly advantageous if delayed, modulated signals aregenerated from the carrier-frequency signal, and if the delayed,modulated signals are mixed with received signals. The radar device maytherefore operate according to the correlation method. For instance, thedistance of a target object may be inferred by correlation on the basisof the time delay from the emission to the reception of the radarpulses.

[0028] Usefully, the radar pulses are emitted by a single transmittingantenna. It is thus sufficient that different directionalcharacteristics are generated by an antenna array on the receiver end,while a single transmitting antenna is provided on the transmitter end.

[0029] It may likewise be advantageous if the radar pulses are emittedby an array having a plurality of antennas. These antennas may bepositioned separate from the antenna array on the receiver end, or theymay be identical with the antenna array on the receiver end. Thus, thereis great flexibility within the scope of the present invention withrespect to the layout of transmitting and receiving antennas.

[0030] Moreover, it is particularly useful within the framework of thepresent invention if a high pulse repetition frequency is generated andif a low pulse repetition frequency is generated. The different pulserates may therefore be utilized for different applications, thedifferent pulse repetition frequencies being used on the variousdirectional characteristics.

[0031] In this connection, it is particularly advantageous if the lowpulse repetition frequency is produced by dividing the high pulserepetition frequency by a whole number. Pulse repetition frequencies arethereby advantageously available which have an integer relationship.Generating the various pulse repetition frequencies in this manner isalso efficient.

[0032] Preferably, the radar pulses having the wide directionalcharacteristic are emitted with the high pulse repetition frequency, andthe radar pulses with the swivelling directional characteristic areemitted with the low pulse repetition frequency. For example, duringthis operation, it is possible to perform the time-critical measurementon the wide directional characteristic using a high pulse repetitionfrequency, while for the swivelling directional characteristic, which ispreferably less time-critical within the framework of the presentinvention, it is possible to work with the lower pulse repetitionfrequency.

[0033] The radar pulses with the swivelling directional characteristicare preferably emitted using a pulse repetition frequency that ismodulated by a PN (“pseudo-noise”) code. When working with such a PNmodulation, it is decided according to a PN code whether a pulse is sentor not. Since the PN code is known to the receiver, a target object maybe detected by correlation.

[0034] The present invention is based on the surprising finding that aplurality of sensor applications may be implemented concurrently in onesensor using different directional characteristics. A flexibleadaptation of the directional characteristic to the specific applicationmay be carried out during the operation. The radar device of the presentinvention may provide an angular resolution, thereby making it possibleto reduce the total number of sensors in a motor vehicle. Thesignal-to-noise ratio (S/N) is improved, since a plurality of antennasis used on the receiver end. Moreover, the signal-to-noise ratio may beincreased in the manner that the average power is raised by increasingthe pulse repetition frequency, such an increase in the pulse repetitionfrequency being possible depending on the practical application. Asimultaneous increase of the pulse repetition frequency and a loweringof the peak pulse power, relevant for approval, may then lead to aretention of the signal-to-noise ratio, while at the same time, however,the electromagnetic compatibility of the radar device is increased.Improvement of the electromagnetic compatibility, that is to say, theability of an electrical device to function satisfactorily in itselectromagnetic environment without unacceptably influencing theenvironment to which other devices also belong, has advantages in viewof the approval of the device before regulating authorities. It maylikewise be advantageous that, given joint use of the antenna array as atransmitting and receiving antenna, the sensor on the whole is reducedin size.

BRIEF DESCRIPTION OF THE DRAWING

[0035] The present invention shall now be clarified by way of example interms of preferred specific embodiments, with reference to theaccompanying Drawing, in which:

[0036]FIG. 1 shows a schematic representation of a first specificembodiment of a radar device according to the present invention; and

[0037]FIG. 2 shows a schematic representation of a second specificembodiment of a radar device according to the present invention.

DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

[0038]FIG. 1 shows a schematic representation of a first specificembodiment of a radar device according to the present invention. Acarrier frequency, e.g. 24 GHz, is generated by a local oscillator 10.This carrier frequency is modulated in a transmission branch. Themodulation is carried out by a pulse-shaping 12 which is connected to acontrol 42. This pulse-shaping element 12 actuates modulation means 14,so that modulated radar pulses having a specific pulse repetitionfrequency arrive at transmitting antenna 16. Transmitting antenna 16radiates the radar pulses with a wide directional characteristic 36.After being reflected on a target object, the radar pulses are receivedby a receiving device. A plurality of antennas 18 a, 18 b, 18 c, 18 d isprovided which receive the reflected radar pulses. Due to the subsequentswitching operation in the reception branch, antennas 18 a, 18 b, 18 c,18 d are able to operate with different directional characteristics.Thus, for example, a wide directional characteristic 32 or a narrowdirectional characteristic 34 may be made available. In addition, narrowdirectional characteristic 34 may be swivelling. The received radarpulses are processed in such a way that the radar pulses are initiallyconveyed to a 3 dB-divider, so that different reception branches 24, 26are obtained. In the first reception branch, means 28 a, 28 b, 28 c, 28d are provided for modulating the phase and the amplitude of thereceived radar pulses. Means 30 a, 30 b, 30 c, 30 d for modulating thephase and the amplitude of the radar pulses are likewise provided insecond reception branch 26. These means are influenced by control 42 inthe manner that the specific directional characteristics are obtained inreception branches 24, 26. The resulting signals are supplied in firstreception branch 24 to a first mixer 48. In second reception branch 26,the resulting signals are supplied to a second mixer 50. Both mixers 48,50 receive modulated carrier-frequency signals, the modulation beingeffected by a pulse-shaping 13, connected to control 42, and modulationmeans 15. In this way, a correlation is obtained, and finally thefurther evaluation of the radar pulses may be carried out, i.e caused,in control 42. For example, swivelling directional characteristic 34 onthe receiver end may be used for an operation with regard to ACC stop &go. By the swivelling of narrow directional characteristic 34, angleinformation is obtained with respect to the target objects. Since theACC stop & go operation is not generally particularly time-critical,there is sufficient time for swivelling the reception lobe. In contrast,the precrash operation is extremely time-critical, so that here widedirectional characteristic 32 is used on the receiver end.

[0039] In the present example according to FIG. 1, two receptionbranches are provided. It is likewise possible to provide more than tworeception branches; more than two directional characteristics may alsobe implemented. Therefore, the directional characteristics may beoptimized depending on the practical application.

[0040] Moreover, it should be noted that the precrash and the ACC stop &go applications are only examples of applications which are typical fora time-critical and an angle-critical application, respectively. Thepresent invention may likewise be utilized for the parallel, optimizedoperation of other practical applications.

[0041]FIG. 2 shows a schematic representation of a further specificembodiment of a radar device according to the present invention.Elements which correspond to those from FIG. 1 are designated by thesame reference numerals. In the specific embodiment according to FIG. 2,antenna array 18 a, 18 b, 18 c, 18 d is used both for transmitting andfor receiving operation. Preferably, different pulse repetitionfrequencies are used on the various directional characteristics. Thesedifferent pulse repetition frequencies are realized by the interactionof control 42 with pulse-shaping 12 a, 12 b and modulation means 14 a 14b, or by the interaction of control 32 with pulse-shaping 13 a, 13 b andmodulation means 15 a 15 b. Two transmission branches 38, 40 areprovided, the different pulse repetition frequencies being selected sothat the monomode range of the radar device is not violated. In general,the monomode range of a radar device is inversely proportional to thepulse repetition frequency. For example, if a pulse repetition frequencyof 50 MHz is present, a monomode range of 3 m results. This monomoderange may be sufficient to make an adequate precrash operationavailable. However, the monomode range of 3 m is generally notsufficient for an operation with ACC stop & go. Therefore, it ispossible within the scope of the present invention to operate the widedirectional characteristic with a high pulse repetition frequency of,for example, 50 MHz, while a further lower pulse repetition frequency isproduced by dividing the high pulse repetition frequency by a wholenumber. This low pulse repetition frequency is now transmitted onnarrow, swivelling directional characteristic 34. If reception pulseshaving the higher pulse repetition frequency, which were transmitted viathe wide directional characteristic, are now received at the output ofthe narrow directional characteristic, then these errors maynevertheless be eliminated by comparing both channels and based on thedifferent power levels. The monomode range may be increased byswitchover of the two pulse repetition frequencies.

[0042] In this connection, a further possibility of the modulation ofradar pulses is especially worth mentioning. This lies in the emittingof radar pulses, which were modulated with a pseudo-noise code (PN code)with a high pulse repetition frequency, this PN modulation being used onthe narrow directional characteristic. Either a pulse is emitted or not,in accordance with the PN code. Since the PN sequence is known to thereceiver, the object may be detected by correlation.

[0043] Thus, for instance, the following scenario may come about withrespect to the precrash and ACC stop & go applications indicated by wayof example. For the time-critical application (precrash), distance rangeR1 may be scanned, for example, ten times within a time interval T1. Inthe same interval T1, a less time-critical application (ACC stop & go)may at the same time scan a larger distance range R2 (R2>R1) one timeeach at various swivel angles.

[0044] The preceding description of the exemplary embodiments accordingto the present invention is used only for purposes of illustration andnot for the purpose of limiting the present invention. Various changesand modifications are possible within the framework of the presentinvention, without departing from the scope of the invention or itsequivalents.

What is claimed is:
 1. A radar device, comprising means (10) forgenerating a carrier-frequency signal, means (12, 12 a, 12 b, 13, 13 a,13 b) for shaping pulses, means (14, 14 a, 14 b, 15, 15 a, 15 b) forgenerating modulated radar pulses from the carrier-frequency signal,means (16, 18 a, 18 b, 18 c, 18 d) for emitting modulated signals asradar pulses, means (18 a, 18 b, 18 c, 18 d) for receiving radar pulses,and means (20) for processing the received radar pulses, wherein themeans for receiving the radar pulses has an array including a pluralityof antennas (18 a, 18 b, 18 c, 18 d), the means (20) for processing theradar pulses has means for dividing the signal power over at least twodifferent reception branches (24, 26), and means (28 a, 28 b, 28 c, 28d, 30 a, 30 b, 30 c, 30 d, 42) are provided for generating differentdirectional characteristics (32, 34) in the various reception branches(24, 26).
 2. The radar device as recited in claim 1, wherein the means(16, 18 a, 18 b, 18 c, 18 d) for emitting radar pulses have a widedirectional characteristic (36).
 3. The radar device as recited in claim1 or 2, wherein the means (28 a, 28 b, 28 c, 28 d, 30 a, 30 b, 30 c, 30d, 42) for generating different directional characteristics (32, 34)generate a swivelling directional characteristic (34) in at least onereception branch.
 4. The radar device as recited in one of the precedingclaims, wherein the means (28 a, 28 b, 28 c, 28 d, 30 a, 30 b, 30 c, 30d, 42) for generating different directional characteristics in thevarious reception branches (24, 26) generate a wide directionalcharacteristic (32) in at least one reception branch (24, 26).
 5. Theradar device as recited in one of the preceding claims, wherein at leasttwo different transmission branches (38, 40) are provided, and means (28a, 28 b, 28 c, 28 d, 30 a, 30 b, 30 c, 30 d, 42) are provided forgenerating different directional characteristics (34, 36) in the varioustransmission branches (38, 40).
 6. The radar device as recited in one ofthe preceding claims, wherein the means (28 a, 28 b, 28 c, 28 d, 30 a,30 b, 30 c, 30 d, 42) for generating different directionalcharacteristics have a control (42).
 7. The radar device as recited inone of the preceding claims, wherein means (13, 13 a, 13 b, 15, 15 a, 15b) are provided for generating modulated signals from thecarrier-frequency signal, and means (48, 50) are provided for mixing thedelayed, modulated signals with received signals.
 8. The radar device asrecited in one of the preceding claims, wherein the means for emittingthe radar pulses is implemented as a single transmitting antenna (16).9. The radar device as recited in one of the preceding claims, whereinthe means for emitting the radar pulses has an array including aplurality of antennas (18 a, 18 b, 18 c, 18 d).
 10. The radar device asrecited in one of the preceding claims, wherein means are provided forgenerating a high pulse repetition frequency, and means are provided forgenerating a low pulse repetition frequency.
 11. The radar device asrecited in one of the preceding claims, wherein the means for generatinga low pulse repetition frequency divides the high pulse repetitionfrequency by a whole number.
 12. The radar device as recited in one ofthe preceding claims, wherein the radar pulses having the widedirectional characteristic are emitted with the high pulse repetitionfrequency, and the radar pulses having the swivelling directionalcharacteristic are emitted with the low pulse repetition frequency. 13.The radar device as recited in one of the preceding claims, wherein theradar pulses having the swivelling directional characteristic areemitted with a pulse repetition frequency that is modulated by a PN(“pseudo-noise”) code.
 14. A method for operating a radar device,comprising the steps: generating a carrier-frequency signal, shaping ofpulses, generating modulated radar pulses from the carrier-frequencysignal, emitting the modulated signals as radar pulses, receiving ofradar pulses, and processing the received radar pulses, wherein theradar pulses are received by an array having a plurality of antennas (18a, 18 b, 18 c, 18 d), the signal power is divided over at least twodifferent reception branches (24, 26), and different directionalcharacteristics (32, 34) are generated in the various reception branches(24, 26).
 15. The method as recited in claim 14, wherein the radarpulses are emitted with a wide directional characteristic (36).
 16. Themethod as recited in claim 14 or 15, wherein a swivelling directionalcharacteristic (34) is generated in at least one reception branch (24,26).
 17. The method as recited in one of claims 14 through 16, wherein awide directional characteristic (32) is generated in at least onereception branch (24, 26).
 18. The method as recited in one of claims 14through 17, wherein different directional characteristics are generatedin the various transmission branches.
 19. The method as recited in oneof claims 14 through 18, wherein the different directionalcharacteristics are generated by a control (42).
 20. The method asrecited in one of claims 14 through 19, wherein delayed, modulatedsignals are generated from the carrier-frequency signal, and thedelayed, modulated signals are mixed with received signals.
 21. Themethod as recited in one of claims 14 through 20, wherein the radarpulses are emitted by a single transmitting antenna (16).
 22. The methodas recited in one of claims 14 through 21, wherein the radar pulses areemitted by an array having a plurality of antennas (18 a, 18 b, 18 c, 18d).
 23. The method as recited in one of claims 14 through 22, wherein ahigh pulse repetition frequency is generated, and a low pulse repetitionfrequency is generated.
 24. The method as recited in one of claims 14through 23, wherein the low pulse repetition frequency is produced bydividing the high pulse repetition frequency by a whole number.
 25. Themethod as recited in one of claims 14 through 24, wherein the radarpulses having the wide directional characteristic are emitted with thehigh pulse repetition frequency, and the radar pulses having theswivelling directional characteristic are emitted with the low pulserepetition frequency.
 26. The method as recited in one of claims 14through 25, wherein the radar pulses having the swivelling directionalcharacteristic are emitted with a pulse repetition frequency that ismodulated by a PN (“pseudo-noise”) code.